Merge pull request swiftlang#34503 from DougGregor/async-type-lower-void

[async type lowering] Handle Void return from @objc async methods.

Author: DougGregor

lib/SIL/IR/AbstractionPattern.cpp

@@ -532,10 +532,17 @@ AbstractionPattern AbstractionPattern::getFunctionResultType() const {
           callbackResultIndex = 1;
         }
       }
+
+      const clang::Type *clangResultType = nullptr;
+      if (callbackResultIndex < callbackParamTy->getNumParams()) {
+        clangResultType = callbackParamTy->getParamType(callbackResultIndex)
+            .getTypePtr();
+      } else {
+        clangResultType = getObjCMethod()->getASTContext().VoidTy.getTypePtr();
+      }
+
       return AbstractionPattern(getGenericSignatureForFunctionComponent(),
-                          getResultType(getType()),
-                          callbackParamTy->getParamType(callbackResultIndex)
-                                          .getTypePtr());
+                          getResultType(getType()), clangResultType);
     }
 
     return AbstractionPattern(getGenericSignatureForFunctionComponent(),

test/SILGen/objc_async.swift

@@ -1,4 +1,4 @@
-// RUN: %target-swift-frontend(mock-sdk: %clang-importer-sdk) -emit-silgen -I %S/Inputs/custom-modules -enable-experimental-concurrency %s -verify
+// RUN: %target-swift-frontend(mock-sdk: %clang-importer-sdk) -emit-silgen -I %S/Inputs/custom-modules -enable-experimental-concurrency %s -verify | %FileCheck %s
 // REQUIRES: objc_interop
 
 import Foundation
@@ -10,4 +10,7 @@ func testSlowServer(slowServer: SlowServer) async throws {
   let _: Int = await slowServer.doSomethingSlow("mail")
   // CHECK: objc_method {{.*}} $@convention(objc_method) (@convention(block) (Optional<NSString>, Optional<NSError>) -> (), SlowServer) -> ()
   let _: String? = try await slowServer.findAnswer()
+
+  // CHECK: objc_method {{.*}} $@convention(objc_method) (NSString, @convention(block) () -> (), SlowServer) -> ()
+  await slowServer.serverRestart("somewhere")
 }